This invention relates to an apparatus for the connection of a rod, to be used for establishing effective connection between a rod adapted to move linearly in the axial direction and a rotary operating member, typically such as between a lever and an operating rod in the locking mechanism incorporated in an automobile door, for example.
One of the connecting devices of this class heretofore known to the art comprises a head portion having a female screw hole pierced therethrough in the lateral direction, an engaging leg portion extended perpendicularly from the lower side of the head portion, the head portion and the engaging leg portion being integrally molded with a synthetic resin, a rod provided at the terminal portion thereof with a male screw portion matched to the aforementioned female screw hole, and an operating member containing therein a fitting hole for permitting forced entry of the aforementioned engaging leg portion, whereby the required connection of the rod to the rotary operating member is accomplished by helically joining the male screw portion with the aforementioned female screw hole and thereafter causing the engaging leg portion to slide past the fitting hole into rotatable engagement therewith.
The conventional connecting device described above enjoys high fabricability and ready availability at low price, because its principal parts are integrally moldable with a synthetic resin material. Further, it enjoys the advantage that the assemblage of the device is effected with a simple procedure of helically joining the rod with the female screw hole and then inserting the engaging leg portion into the fitting hole of the operating member. Moreover, the fact that the length of the rod can be accurately adjusted by suitably controlling the helical insertion of the rod into the female screw hole adds much to the convenience of the work of assemblage.
Since the aforementioned device is formed of a synthetic resin material, however, it fails to provide fully reliable strength as needed when it is used in a connection mechanism operated with high frequency and exposed to heavy load. Particularly in case where the male screw portion of a metal rod is helically joined with the female screw hole, there ensues a fair possibility that the female screw hole, because of its material, will tend to sustain damage. Besides, in the case of the engaging leg portion intended for engagement with the fitting hole of the operating member, the slit cut into this leg portion for the purpose of decreasing the force required for its insertion in the process of the engagement can deprive the leg portion of its force of engagement possibly to a point where the leg portion will fall off the hole or snap.
Further the conventional device described above does not tolerate any change in the diameter of the rod because the female screw hole to which the rod is connected is directly bored in the head portion. Thus, it has the disadvantage that the rod to be used in the device is required to have a fixed diameter.